To check out the new feature, make sure you've updated to the latest version of Firefox, then type about:config into the address bar. Promise Firefox you'll be careful, then search for social.enabled using the about:config search bar. Double-click the social.enabled option to set it to True. You should find that you have Facebook notifications for friend requests, messages, and other posts in the upper right-hand corner of your browser. It may not be the best way to stay productive, but it's nice to have.

Unfortunately, it also adds a chat sidebar and mini-feed to the side of your browser, making this a deal killer for most people (including myself). If you spend a lot of time on Facebook chat, I could see it being handy to chat from any window you want, but you can remove this by going back to about:config and setting social.sidebar.open to false. Thanks to Stephen and Mark Molinyawe for sharing that second tweak!